Amino-containing materials such as amino-containing analytes, amino acids, DNA, RNA, proteins, cells, tissue, organelles, immunoglobins, or fragments thereof immobilized on a surface of a substrate can be used in numerous applications. For example, immobilized biological amino-containing materials can be used for the medical diagnosis of a disease or genetic defect, for biological separations, or for detection of various biomolecules. Immobilization of the amino-containing material is typically accomplished by reaction of the amino group with a reactive functional group that is covalently attached to the surface of the substrate.
Substrates having amino-reactive functional groups can be prepared by coating a substrate with a solution of a polymeric material that contains amino-reactive functional groups. Alternatively, substrates having amino-reactive functional groups can be prepared by coating a substrate with a solution of monomers that contain amine reactive functional groups followed by polymerization of the monomers. Exemplary amino-reactive monomers include, for example, N—[(meth)acryloxy]succinimide and vinyl azlactone. An amino-containing material can react with the N-acyloxysuccinimide group resulting in displacement of N-hydroxysuccinimide and formation of a carboxamide. An amino-containing material can react with the cyclic azlactone resulting in an opening of the ring structure.
Although polymeric surfaces that include a reactive functional group such as an N-acyloxysuccinimide group or an azlactone group can react readily with primary or secondary amino-containing materials, such reactive functional groups can suffer from a number of disadvantages. For example, many of the reactions with biological amino-containing materials are conducted in dilute aqueous solutions. Under these conditions, the N— acyloxysuccinimide functional group is known to undergo rapid hydrolysis. This competing reaction can cause incomplete or inefficient immobilization of the amino-containing materials on the substrate.
While azlactone functional groups are more stable to hydrolysis, it is difficult to synthesize an azlactone linked to any polymerizable group other than a vinyl group. The resulting polymeric material has amino-reactive functional groups directly attached to the polymer backbone. In some applications, this can make it difficult for the amino-containing material to get close enough to the amine reactive group for efficient immobilization.